One example of conventional fluid transfer devices is shown in FIG. 2 (see PTL 1, for example). As shown in FIG. 2, a fluid transfer device 1 includes: first and second tanks 3 and 4 each configured to store a fluid 2 containing fine powder; a pipe 5 configured to cause the first tank 3 and the second tank 4 to communicate with each other and including a flexible tube portion 5a partially having flexibility; and roller portions 6 capable of rotating in both forward and backward directions and configured to rotate and press the flexible tube portion 5a to cause the fluid 2 in the flexible tube portion 5a to move in the forward or backward direction.
As shown in FIG. 2, the roller portions 6 are respectively provided at both end portions of a revolving arm 7. The flexible tube portion 5a is arranged along an inner surface of a U-shaped cross section of a recess 8a formed in a housing 8.
According to the fluid transfer device 1, by causing the revolving arm 7 to rotate in a desired direction, the roller portions 6 rotate and press the flexible tube portion 5a. Thus, the fluid 2 in the flexible tube portion 5a can be caused to move in the desired forward or backward direction. With this, the fluid 2 in a desired one of the first and second tanks 3 and 4 can be transferred to the other tank.
To be specific, according to the conventional fluid transfer device 1 shown in FIG. 2, the roller portions 6 rotate and press the flexible tube portion 5a to cause the fluid 2 in the flexible tube portion 5a to move in the desired direction. In addition, when the application of a pressing force of the roller portions 6 to the flexible tube portion 5a stops, the flexible tube portion 5a having a flat shape by the pressing is restored to, for example, an original circular cross section by its elastic force. Then, when the flexible tube portion 5a is restored to the original shape, the subsequent fluid 2 moves into the flexible tube portion 5a having the original shape.